Electric hammer



July 8, 1941. T. J. MURPHY ELECTRIC HAMMER Filed 0G13. '22, 1936 uw@ of ATTORNEYSi Patented July 8, 1941 UNITED STATES PATENT OFFECE 2 Claims.

rhis invention relates to an electric hammer and similar electrically operated devices, and has for an object to provide an improved means for reciprocating the hammer element which does not require a large, expensive or complicated auxiliary electrical apparatus.

It is also an object of the invention to provide improved means to maintain the reciproeating element in concentric relation with the magnetic pole members, and to reduce the friction during its travel to a minimum.

Another object is to provide electrical means for reciprocating the element which will give a hard elective blow in proportion to the'amount of energy consumed.

With the foregoing and other objects in view I have devised a construction and arrangement, satisfactory forms of which are shown in the accompanying drawing, but it is to be understood that I am not limited to these specific constructions and arrangements, but that various modifications may be employed within the scope of the invention.

In the drawing:

Fig. 1 is a longitudinal section through a hammer mechanism embodying my invention, the section being substantially on line l-I of Fig. 2;

Fig. 2 is a transverse section thereof, substantially on line 2-2 of Fig. 1;

Fig. 3 is a partial side elevation with parts l broken away of a handle which may be employed for this hammer.

The device as shown comprises two end members or heads l and Il at the opposite ends of a cylindrical shell l2, the heads having flanges in which the ends of the shell are located. The heads are held on the end of the shell by any suitable means such as a plurality of tie rods or bolts i3 extending between the heads within the shell. Located within the shell are laminated magnetic cores lli, these cores extending longitudinally within the shell and having spaced poles l5 extending radially inwardly toward the center. Any desired number of these cores may be used, in the present showing there being eight equally spaced as shown in Fig. 2. These cores are centered Within the shell and in proper concentric relation to the axes of the heads l0 and ll by rings l5 seating in aligned recesses or grooves in the inner surfaces of the heads and the end walls of the cores, the grooves in the heads being preferably V-shaped as shown. Between the inwardly extending poles i5 are located annular coils l1, I8, I9 and 20 of suitable insulated wire.

. in the head l! by a cap 26 within a sleeve 21 mounted to slide in a bushing 28 fixed in the head il. The cap 26 embraces the end of the guide 22 and is itself mounted in the sleeve 21. On guide preferably integral with it, adjacent the head Ill is a flange 29 having a tapered wall or shoulder 33 against which is forced a ring or cap 3i by a heavy spring 32. The other end of this spring is seated in a cup 33 clamped between the shoulder 34 of the guide member and the end Wall of the head I0. The cap or ring 3|' is spaced from the cup 33 so that it is yieldable toward it by compression of the spring 32, but the member 3| extends inwardly of the flange 29 so as to form a stop or abutment for the end of the element 2|. At the opposite end of the guide and slidable on it within the sleeve 21 is another abutment member 35 which projects inwardly a short distance from the inner end of the sleeve 21. Movement of this member 35 is limited by a flange 36 on the member abutting an inwardly extending flange 31 on the inner end of the sleeve 21. Between this member 35 and the cap 26 is a spring 38 tending to move the member 3'5 inwardly against the flange 31 so that this spring causes the member 35 to protrude somewhat outside or beyond the end of the sleeve 21. This spring is a considerably lighter spring than the spring 32.

A drill or `other tool 39 is secured in the holder tu which is centered by means of a projection 6I in the guide 22. This holder as an abutment i2 resting against the end of the cap 26 and this cap has a flange 43 normally held against the end of the sleeve 21 by means of a spring @Ll engaging the flange 43 and secured to the cap Il by any suitable means such as the screws rThe guide member` 22 is preferably hollow and may be provided With a wick or packing i6 to retain a lubricant that is drawn through any suitable located opening 41 to the outside of the guide and thus lubricate its surface.

This central guide means for mounting the reciprocable element or hammer maintains it in centered relation with the operating coils and the magnetic pole members I4 and reduces the friction during its travel to a minimum. A loose fit of element 2l on the central guide member is not necessary, al1 that is required being a good sliding fit. Thus the reciprocating member is always properly centered between the magnetic poles. As the reciprocating element is thus supported and guided in the center its outer surface may be located closely adjacent the magnetic poles I5 without touching them, and it will be seen from Fig. 2, that there is plenty of space around the movable element and between the cores for circulation of air as the element reciprocates, thus allowing free movement of the element, as the air is nowhere pocketed where it is compressed to retard movement of the element.

It will be seen that as the movable or hammer element 2l is reciprocated back and forth its movement to the right is arrested by the abutment member 3l and the heavy spring 32, the

recoil of which starts the member 2l in the opposite direction. The movement of member Si is limited by shoulder 3E). At the other end of its movement the blow of the member 2l is first against the end of the member 35 which yields so that the main force of the blow is against the end 31 of the member 21 by which it is transmitted through the cap 26 to the holder 4S and thus to the tool 3S. The member 35 through the spring 38 assists or starts the return of the hammer element in the opposite direction and thus prevents magnetic sticking of the hammer due to residual magnetism. This central guide continuously assures a uniform gap between the hammer element and the pole pieces. Also as the central guide may be made of a material of high magnetic permeability it assists in lowering the magnetic reluctance of the hardened steel hammer element 2|. The hammer element is preferably made of hardened steel to withstand the eiect of the hammer blows.

The head i0 also includes a handle 4C oonnected to the head by suitable braces 49 and 50, one of which as 49, may be hollow to carry the electrical leads or conductors to the Coils I1 to 20. This handle may also contain a control switch (not shown) for turning on and 01T the current to the coils to thus control the operation.

Having thus set for h the nature of my invention, what I claim is:

l. In a motor of the character described, a central guide member, a reciprocable element embracing said guide and mounted to slide thereon, heads for mounting the opposite ends of sait member, a sleeve mounted to slide in one of said heads and forming an abutment for said element, a second member mounted to move longitudinally of the guide and normally projecting a short distance beyond the abutment to be engaged by the element prior to its hitting the abutment, a spring retaining the second member in said normal position, a tool holder for receiving the force of the blow on the abutment member, and electromagnetic means or reciprocating the element.

2. In a motor E the character described, a guide member, a reciprocable element mounted to slide thereon, a head mounting one end of said guide, an abutment slidable in the head to receive the blows of the element, a second member movable longitudinally of the guide and normally projecting beyond the abutment to be engaged by the element before it hits the abutment, yieldable resilient means holding the second member in said normal position, a tool holder receiving the force of the blow from the abutment member, and electromagnetic means for reciprocating the element.

THOMAS J. MURPHY. 

